3D audio is realized by providing a sound scene (2D) on a horizontal plane, which existing surround audio has provided, with another dimension in the direction of height. 3D audio literally refers to various techniques for providing fuller and richer sound in 3-dimensional space, such as signal processing, transmission, encoding, reproduction techniques, and the like. Specifically, in order to provide 3D audio, a large number of speakers than that of conventional technology are used, or alternatively, rendering technology is widely required which forms sound images at virtual locations where speakers are not present, even if a small number of speakers are used.
3D audio is expected to be an audio solution for a UHD TV to be launched soon, and is expected to be variously used for sound in vehicles, which are developing into spaces for providing high-quality infotainment, as well as sound for theaters, personal 3D TVs, tablet PCs, smart phones, cloud games, and the like.
Meanwhile, MPEG 3D audio supports a 22.2-multichannel system as a main format to provide high-quality service. This is a method proposed by NHK, in which top and bottom layers are added to form a multi-channel audio environment because surround channel speakers at the height of the user's ear level are not enough to provide such a multi-channel environment. In the top layer, a total of 9 channels may be provided. Specifically, a total of 9 speakers are arranged in such a way that 3 speakers are arranged at the front, center, and back positions. In the middle layer, 5, 2, and 3 speakers are respectively arranged at the front, center, and back positions. On the floor, 3 speakers are arranged at the front, and 2 LFE channels may be installed.
Generally, a specific sound source may be located in the 3-dimensional space by combining the outputs of multiple speakers (Vector Base Amplitude Panning: VBAP). Using amplitude panning, which determines the direction of a sound source between two speakers based on the signal amplitude, or using VBAP, which is widely used for determining the direction of a sound source using three speakers in 3-dimensional space, rendering may be conveniently implemented for the object signal, which is transmitted on an object basis.
In other words, a virtual speaker 1 may be generated using three speakers (channel 1, 2, and 3). VBAP is a method for generating an object vector in which the virtual source will be located based on the position of a listener (sweet spot), and the method renders a sound source by selecting speakers around the listener and calculating a gain value for controlling the speaker positioning vector. Therefore, for object-based content, at least three speakers surrounding the target object (or the virtual source) are determined, and VBAP is reconfigured according to the relative positions of the speakers, whereby the object may be reproduced at a desired position.